The purpose of the Mutant Animal Breeding (MAB) Core is to provide research subjects for the components of the center. The MAB Core will establish and maintain lines of genetically manipulated mice that are essential for the research objectives of the components. This core is necessitated because the majority of the genetically modified mice will be produced by Component by Kieffer, which is located in France. The other Components are on the UCLA campus, where the core will be housed, and will need a reliable supply of these mice. The core will breed heterozygous mice so that the components can be supplied with homozygous mutants and littermate wild type controls. Heterozygous animals can also be provided as necessary, while additional heterozygotes will be used as breeders. All experimental animals and breeding stocks will be tracked with a computerized pedigree. To guard against genetic drift, every 10 generations we will purchase pure male C57BL/6 mice from a commercial supplier and breed them with our heterozygous females. The resulting heterozygotes will be bred with MAB Core heterozygotes in the next round of breeding. The MAB Core will make extensive use of the Molecular Biology Core for genotyping.